The present invention relates to elastomers containing a filler or plurality of fillers that can be magnetically aligned in such a way that products formed by such elastomers present a useful magnetic field in a similar manner to a permanent or electro magnet. These magnetically-filled elastomers can be thermo-plastically formed, thermoformed, or formed as a result of a thermosetting reaction. The present invention also relates to methods for aligning the magnetic fillers in these elastomers. An embodiment of the present invention particularly relates to the provision of magnetically-filled polyurethane elastomers. Furthermore, the present invention relates to the employment of elastomers and, more particularly, magnetically-filled elastomers in vibration dampening devices.
It is well known that particles of certain pure metals, namely iron, cobalt, and nickel, can be treated in such a way that their magnetic moments or domains become aligned and said particles then behave as magnets, that is, they acquire a magnetic field within which magnetic materials may be influenced as to their energy content and potential. The strength of the field increases according to the percentage of the domains present and those aligned. The field can be further increased by the addition of other metals or their oxides to form magnetic alloys, as, for example, by the addition of barium, boron, cobalt, copper, iron, neodymium, nickel, promethium, samarium, and strontium, and alloys thereof. Trialloys, such as neodymium-iron-boron, can also be formed to further increase the field strength.
Another group of suitable magnetic materials consists of ferrites, as, for example, lodestone. These include the oxides of iron to which small quantities of transition metal oxides such as cobalt or nickel have been added. These are known as spinel ferrites and have the general formula M(OFe2O3) where M is a divalent transition ion. Another form of ferrite is iron oxide to which the oxides of the reactive metals strontium or barium have been alloyed. Ferrites are particularly useful because they are easily reduced to a powder and can be reformed to suitable shapes by compaction or as a component of a plastic or ceramic compound. However, the present invention is not restricted to the use of magnetic material in the form of lodestone or oxides of iron, although these are often preferred because of cost, coercivity, achievable field strength, and ease of reconstitution or molding. Alternatives include, but are not restricted to, the primary magnetic elements as discussed above, namely, cobalt, iron, nickel and alloys that include barium, boron, cobalt, copper, iron, neodymium, nickel, promethium, samarium, strontium, and alloys thereof. Examples of suitable alloys are cobalt-samarium and neodymium-iron-boron.
Advantageously, such magnetic material can be machined into special shapes or reduced to a free-flowing powder, sometimes as fine as 600 mesh, and reconstituted by introducing a binder, sintering under pressure, or by introducing the powder as a component of a compound that at some stage becomes liquid and subsequently solidifies. Such carriers can range from glass to wax in natural conversion processes and from ceramics to plastics in synthetic systems. Other suitable matrices for carrying such magnetic material include natural and synthetic woven and non-woven materials, flexible plastic, and various forms of foam and rubber. In the prior art, such carriers produce substantially rigid magnets. In the present invention, it has been found that magnetic fillers may be incorporated into thermoplastic and thermosetting elastomers to provide physically soft elastomer-based magnets that produce a useful magnetic field.
It has also been found that the field strength of such elastomer-based magnets is a function of the coercivity of the magnetic filler and its packing density. The packing density has been found to be dependent on the particle shape of the filler, its surface texture, and the nature or melt viscosity of the carrier elastomer. Consequently, it is one object of this invention to mold components that exhibit the maximum possible field strength commensurate with the packing density of the magnetic filler. Methods for aligning the magnetic filler within the elastomeric matrix in order to increase the packing density and resultant magnetic field are also disclosed.
Additionally, lightweight filler materials may be employed in the present invention. It has been found that reinforcing lightweight filler materials may be advantageously employed in the compositions of the present invention because they perform the dual function of reducing the overall density and improving the mechanical strength of the composite.
When magnetic material is incorporated into a typical rubber matrix, the resultant product""s hardness is generally about 60 on the Shore A scale. In the prior art, plastic- and rubber-based magnets have been made flexible by casting in them in very thin cross-section, in which case, however, the field strength is usually impractically low. To overcome this low field strength, the magnetic sheet is often rolled to form a round or square section tube, resulting in an almost total loss of cross-sectional flexibility while retaining such longitudinal flexibility as to make them useful for gaskets, including domestic appliances such as refrigerators where curvature is gentle and sharp bends are catered for by mitre jointing.
It has been found that magnets of higher strength, that is of thicker cross-section, are capable of attracting the hemoglobin content of erythrocytes present in blood plasma. Such magnets may be strategically placed in medical devices to attract erythrocytes to various parts of the body to increase the oxygen supply to that point. In use, these magnets are embedded in or attached to rubber, plastic, cloth or other materials to hold them in place.
It should be appreciated that, in the prior art, these magnets are necessarily small in diameter, comparatively large in cross-section, and of a hardness at least measurable at about 50 on the Shore A scale. Such magnets must be cushioned if they are placed near to soft tissue, and any barrier between the field source and such soft tissue will reduce the effective field strength of the magnet. Thus, in one embodiment of the present invention, soft, energy dissipating, polyurethane elastomer compositions containing magnetic material are provided for comfortable employment in medical devices for the purpose of attracting the hemoglobin present in blood plasma. These polyurethane elastomer compositions can be worn next to soft tissue without interfering with the comfort or well being of the wearer as they are capable of deflecting easily but with a limited degree of permanent compression and with a predetermined recovery rate similar to that of the soft tissue with which they are going to closely function. A preferred elastomeric composition useful for such devices is an additional embodiment of the present invention.
The thermosetting and thermoplastic elastomeric compositions of the present invention have also been found to be useful in vibration dampening systems. More specifically, it has been found that visco-elastic polymers derived from elastomers of the present invention can advantageously be employed in vibration dampening devices.
In an embodiment of the present invention, a simple vibration dampening device having upper and lower constraining components that are influenced by at least one separating layer of a magnetically charged elastomer is provided. Preferably, the elastomer is a visco-elastomer as discussed hereinabove. However, it has been discovered that the elastomer need not be magnetically-filled to be useful in the vibration dampening systems of the present invention although such elastomers are preferred.
The introduction of a magnetically active substance into the elastomer presents an additional facet to the control of dampening devices in that the magnetically active component of the elastomer may be polarized to react with the constraining layers or with themselves if constructed in separate or opposing layers. Also provided is a vibration dampening device wherein a spring is encapsulated in an elastomer that may or may not be magnetically filled.
In light of the foregoing, it is an object of the present invention to provide thermoplastic and thermosetting elastomers containing magnetic fillers that are capable of alignment by static or electromagnetic means.
It is another object of the present invention to provide elastomers, as above, wherein the magnetically-filled elastomers exhibit the maximum possible field strength commensurate with the packing density of the filler.
It is a further object of the present invention to provide elastomers, as above, wherein the magnetic filler is aligned to maximize its packing density.
It is an additional object of the present invention to provide elastomers, as above, wherein the shape and surface texture of the magnetic filler is modified to increase the packing density.
It is still an object of the present invention to provide elastomers, as above, containing lightweight filler materials to reduce the overall density of the elastomer composite and/or improve its mechanical strength.
It is yet another object of the present invention to provide a process for the alignment of magnetic filler within an elastomeric matrix.
It is also an object of the present invention to provide a preferred elastomeric composition for use as the elastomeric matrix for packing of the magnetic fillers.
It is still another object of the present invention to provide vibration dampening device that utilizes an elastomer composition.
It is still another object of the present invention to provide magnetically-filled elastomer compositions for employment in vibration dampening devices.
It is also an object of the present invention to provide a vibration dampening device wherein at least one elastomer or magnetically-filled elastomer composition is affixed to at least one constraining layer.
It is additionally an object of the present invention to provide a vibration dampening device, as above, wherein the elastomer, whether or not magnetically filled, is a visco-elastomer.
It is yet a further object of the present invention to provide a vibration dampening device, as above, wherein each constraining layer and each of the at least one magnetically-filled elastomer or visco-elastomer compositions is dynamically attracted or opposed to its adjacent layer.
It is still yet another object of the present invention to provide a vibration dampening device having a spring encapsulated in an elastomer, magnetically-filled elastomer, or magnetically-filled visco-elastomer.
These and other objects of the present invention, as well as the advantages thereof over existing prior art forms, which will become apparent from the description to follow, are accomplished by the improvements hereinafter described and claimed.
In general, a compound made in accordance with the present invention includes an elastomer selected from the group consisting of thermosetting elastomers and thermoplastic elastomers, and a magnetic filler capable of alignment and energizing before, during, or after the molding of the elastomer.
Other objects of the present invention are accomplished by a compound containing magnetic filler capable of alignment and energizing before, during, or after the molding of the compound, which is the reaction product of a urethane-forming component and a diisocyanate reacted in less than stoiciometric amounts, wherein the urethane-forming component comprises a compound containing at least two urethane-forming reactive sites and capable of forming stable complexes through unreacted urethane-forming reactive sites, and an elasticizing polyol selected from the group consisting of diols and triols.
Additional objects of the present invention are accomplished by a vibration dampening device that includes at least one elastomer layer affixed to at least one constraining layer. Further objects are accomplished when the elastomer is a magnetically-filled elastomer.
Preferred exemplary embodiments incorporating the concepts of the present invention are shown by way of example in the accompanying drawings without attempting to show all the various forms and modifications in which the invention might be embodied, the invention being measured by the appended claims and not by the details of the specification.